/*
 * Copyright (C) 2007 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import java.util.Map;

import javax.annotation.Nullable;

import com.google.common.annotations.GwtCompatible;

/**
 * A map, each entry of which maps a Java <a
 * href="http://tinyurl.com/2cmwkz">raw type</a> to an instance of that type. In
 * addition to implementing {@code Map}, the additional type-safe operations
 * {@link #putInstance} and {@link #getInstance} are available.
 * 
 * <p>
 * Like any other {@code Map<Class, Object>}, this map may contain entries for
 * primitive types, and a primitive type and its corresponding wrapper type may
 * map to different values.
 * 
 * @param <B>
 *            the common supertype that all entries must share; often this is
 *            simply {@link Object}
 * 
 * @author Kevin Bourrillion
 * @since 2010.01.04 <b>stable</b> (imported from Google Collections Library)
 */
@GwtCompatible
public interface ClassToInstanceMap<B> extends Map<Class<? extends B>, B> {
    /**
     * Returns the value the specified class is mapped to, or {@code null} if no
     * entry for this class is present. This will only return a value that was
     * bound to this specific class, not a value that may have been bound to a
     * subtype.
     */
    <T extends B> T getInstance(Class<T> type);

    /**
     * Maps the specified class to the specified value. Does <i>not</i>
     * associate this value with any of the class's supertypes.
     * 
     * @return the value previously associated with this class (possibly
     *         {@code null}), or {@code null} if there was no previous entry.
     */
    <T extends B> T putInstance(Class<T> type, @Nullable T value);
}
